In the present description and in the following claims, the term “framing” is used to mean the operation by which a relatively stable geometry is conferred to a motor-vehicle body formed by elements of pressed sheet-metal or to a sub-assembly thereof. Typically this operation is carried out by applying a plurality of welds or clinched joints or riveted joints to a body comprising a lower sub-assembly or floor panel, two side portions connected to the floor panel at the two sides thereof and two or more cross-members which connect the side portions at their top. The welds/clinched joints/riveted joints can be carried out for instance manually or preferably by means of programmable robots provided at a framing station, where the component parts of the body are precisely located in position and clamped until the framing operation is completed. It is well understood that the present invention is applicable both to plants in which the framing operation is carried out at a single station, and to plants in which the framing operation is carried out at many stations arranged after each other, in which case the principles of the invention may be used also at framing stations which operate on bodies which have been already preliminarly framed.
Framing systems for motor-vehicle bodies have been known and used since long, which comprise a framing station and a conveyor line for supplying the framing station with a sequence of lower body sub-assemblies or a sequence of preassembled bodies, and for bringing the framed bodies out of the framing station. The framing station comprises locator means for locating and clamping the component parts of a body in the proper assembling position, and assembling means for applying a plurality of welds or clinched joints or riveted joints to the located and clamped body. The afore-said locator means comprises at least one pair of locating and clamping structures provided at the two sides of the line at the framing station, each pair of side structures being provided with a plurality of locating and clamping devices for engaging the component parts of a motor-vehicle body or a sub-assembly thereof, said locating and clamping devices being shaped and arranged so as to be adapted to a specific model of motor-vehicle body. The afore-said side locating and clamping structures are displaceable along a direction transverse with respect to the conveyor line, between a closed operative condition, in which they are relatively closer to each other, to engage the component parts of the body which is at the framing station, and an opened operative condition, in which said side locating and clamping structures are more spaced apart from the line, to enable activation of the conveyor line in order to replace a framed body with a new body to be framed at the framing station and/or to enable, if necessary, the component parts of the side portions of a body to be prepared on the two side locating and clamping structures.
The applicant company has been manufacturing and marketing for a long time framing systems of the above indicated type under the trademarks ROBOGATE and OPEN ROBOGATE. Some of the most recent embodiments have been disclosed in European patent applications EP-A-1 611 991, EP-A-1 686 048, EP-A-1 837 120, EP-A-1 897 653, EP-A-1 918 182 and EP-A-1 935 554.
The framing systems of the above indicated type have the relevant advantage to be easily adapted to operate on different types or models of motor-vehicle bodies. To this end, many pairs of side locating and clamping structures are provided which are rapidly interchangeable with each other at the operative position in the framing station. Each pair of these structures is provided with locating and clamping devices shaped and arranged so as to conform with the shape and the dimensions of a specific body model. Due to these features, the framing stations is thus able to operate in a flexible way on any possible mix of different types or models of bodies which are advanced along the line, so as to enable a quick adaptation of the production to the demand from the market, while also ensuring a uniform assembling quality, given that all the bodies of a same type are located and clamped precisely during assembling by means of the same locating and clamping devices.
However, limitations exist to the degree of flexibility of the framing systems which have been made and used heretofore. In particular, limitations exist with regard to the admissible variations in the longitudinal length and/or in the transverse width of the different types of bodies on which the framing station is able to operate.
A system as indicated in the preamble of claim 1 is known from EP-A-1 611 991. A flexible framing station with movable locators is also known from GB-A-2 151 991.